Photographic color correction process



1946. LE ROY M. DEARING v 3 3 PHOTOGRAPHIC COLOR CORRECTION PROCESSFiled larch 6, 1942 BFUSURE F 5 R BLUE SENS/WVE EMULSION.

g E R- l3 GREEN SEN6I77VEEMUL5IOM fi RED SENSITIVEEMULSION.

l0 REDSEN-SITIVEEMULSION WITH COUPLER.

, COMB/NED 8LACK-AND-HHITEAND if cow/2 DEVELOPMENTI m$lw REVERJALEXPOSURE, COL OR OEVELOPMEN T AND REMOVAL OF. SIL VER AND SIL VER SALTS.

' amsz/RE FIG-Z BLUE SENSITIVE EMULSION NIT H f} ggay cg ge 26 WW REDAND INFRI-I-RED SENSITIVE 25 if! EMULSION.

. REEN SENSITIVE EMULSION wrm MAGENTA COUPLER. RED SENSITIVE EMULSIONNITH CVAN COUPLER.

COLOR DEVELOPMENT.

INFRA -RED FLASH, cow/e DEVELOPMENT, g gI/AL 0F 67L VER AND SILVER VLEROYMDEIRING INVENTOR Patented Jan. 29, 1946 UNITED STATES PATENTOFFICE rno'roonnrmo COLOR CORRECTION PROC Le Roy M. Bearing, Rochester,N. Y., asslgnor to Eastman Kodak Company, Rocheate r, N. 'Y., a

corporation of New Jersey Application March 6, 1942, Serial No. 433,6422 Claims. (c1. 95-2) This invention relates to processes ofsubtracprocesses the three dyes are not equally bad in this respect, thefinal result of printing such a film is to introduce unequal parts ofallthree records in each image which is made, regardless of the color oflight used in printing or the sensitivity of the photographic materialsused. In a typical case, where less magenta o yellow dye is used and thegray scale is maintained by the blue-greens, the greens, blues and cyansof a print may be degraded with gray and are less luminous than theyshould be, while the magentas, yellows, and reds are lacking in 'satura,tion by virtue of dilution with white.

In the past, methods for compensating for the deficiencies of dyes inphotographic subtractive color films have consisted of producingsuitable metallic masks by exposure of a sensitive layer through dyeimages in an incorrectly color-balanced film and developing a maskingimage in the exposed layer. If properly exposed and developed theresultant silver image will compensate for the lack of color balance inthe subtractiveiy colored film when the image is placed in register withthe dye images. Processes of this type have been described in Mannes,Godowsky, and Wilder U. S. Patent 2,258,187, granted October 7, 1941,and Evans U. S. patent application, Serial No. 413,442, filed October 3,1941, and Hanson U. S. Patent 2,336,243, granted December 7, 1943. Thesereferences describe the formation of a masking image in a maskingemulsion layer after the formation 01 color images in the film, byexposure through the dye images, the quality of the masking image beingdetermined by the characteristics of the dye images in the incorrectlycolorbalanced film. The quality of the masking image is, therefore, onlyindirectly dependent on the original scene or object photographed.

The present invention ha for one of its objects, providing a method ofcolor correction wherein the quality and degree or the masking image isdetermined directly by the original obiect exposure. Othe objects willappear herematter.

In the accompanying drawing, means for accomplishing the objects of myinvention are il-- lustrated. Fig. 1 of the drawing is a flow diagramillustrating the method of applyingmy invention to a reversal process ofsubtractive color photography. Fig. 2 illustrates by means of a newdiagram a method of applying my invention to a negative-positive processof subtractive color p oto r p y:

My invention is especially adapted to correction for deficiencies indyes of the type'previously mentioned, wherein the greensare degradedwith gray and the reds are desaturated. To correct for these errors useis made of masking layers incorporated in an original film or in aduplicate film. Images in the masking layers balance the transmission ofthe subtractive dyes by either giving extra exposures to those areascovered by cyan and magenta or by placing density over areas covered byother colors.

My invention, as applied to reversal processes,

will now be described by particular reference to the accompanyingdrawing.

In reversal processes of subtractive color photography, the generalprocedure is to record images in superposed differentially sensitizedemulsion layers-and after development r a negative stance in Mannes andGodowsky U. S. Patent No.

2,252,718, granted August 19, 1941, Jelley and Vittum U. S. Patent2,322,027, granted June 15, 1943, and Mannes and Godowsky U. S. Patents2,304,939 and 2,304,940, granted December 15, 1942.

The first stage of Fig. l of the accompanying drawing shows a, film ofconstruction similar to.

that of the prior art cited but containing an extra, masking layer,which film may be used in the present invention. A support ill of acellulose ester or other similar material; has coated upon it the redsensitive emulsion layer ll containing; a coupler compound. This layeris designedgto Over the masking; layer H are levers l2, l3, and H whichare-red receive a masking. image.

green, and blue sensitive emulsion layer spectively. The yellow filterlayer li.;separates: the blue sensitive emulsion layer fromathe .red.and green sensitive emulsions. flhe, {coupler pler compounds capable ofI exposure of layer ordinary black-and-white developer.

' compound contained in the masking layer I I may,

for instance, be cyanoacetanilide p-benzyl phenol or othenn'on-diflusingor protected coucoupling with the oxidation product of a developer togive a, neutral gray or colored dye image. The emulsion layer I I isgiven a different type of red sensitivity than that of layer I2, in therespect that the red sensitizer of layer II is capable of beingdestroyed in first development. A red sensitizersuitable for thispurpose is pinacyanol. In addition, the emulsion has a higher blue speedthan the red and green sensitive emulsion layers I2 and I3. Afteroriginal exposure of the film to a colored object, it is treated with adeveloping solution of the following typical composition:

Sodium sulflte grams sodium hydroxide ..do 5 z-amino-fi-diethyl aminotoluene hydrochloride grams' 2 p-Methyl amino phenol sulfate ....do 2Water to -..cc 1000 As may be seen, this developer contains, in additionto the ordinary black-and-white developing agent, a developing compoundthe oxidation product of which will couple with the coupler compound inlayer I I to give a dye image in the region of the red aspect silverimage. The film now appears as shown in the second stage of Fig. 1wherein the differentiall sensitive emulsion layers I2, I3, and I4contain in the respective layers negative silver images IS, IT, and I8.The masking layer -II contains the silver'and dye image In case thecoupler compound in layer II was cyanoacetanilide the masking image I9would the coupler compound in the layer was p-benzyl phenol a neutralgray dye image would be formed. In certain cases it is desirable to usetwo developers in place of the above, in which case after originalexposure, the film is developed in a color developer, as for inbe purplein color. If

stance, solution A shown later in the specifics.

tion, followed by an ordinary black-and-white developer. Subsequentprocessing steps include I2 to red light and development of a cyan imagein the layer by use of a cyan coupler developer such as disclosed in U.S. Patent No. 2,252,718, followed by exposure of layer II to blue lightand development to silver in an Thereafter, the green and blue sensitiveemulsion layers I3 and I4 are re-exposed and color developed in magentaand yellow coupler developer solutions as described in the patent abovecited. Thereafter, the silver and any residual silver halide is removedwith a ferricyanide bleaching solution followed by a fixing solution.The film now appears as shown in the third stage of Fig. '1 wherein thepositive dye images 2|, 22, and 23 are colored cyan, magenta and yellowrespectively. The masking layer contains the dye image 20. In a similarmanner it may be shown that the above-described process is effective inplacing masking density over areas of the color film transmittingmagenta. and yellow picture images.

-If the corrected transparency is to be used as an original film forduplicating, the negative masking image can be of any color as long as acomplementary colored filter of equivalent densityis'used in theprinting beam. It is preferred that the masking dye image be less stablein acid or alkaline solutions than the dyes making up the picture imagesin order that the mask ing dye my be removed without damage to the colordyes if a clear transparenc without a mask is desired at some laterdate. To this end, coupiers may be chosen for the masking layer whichwill give a dye that can be removed by weakly acid, strongly basic,moderately reducing or oxidizing baths.

' A variety of other methods may be employed for forming the maskingimage in the masking layer II without forming a dye image in thepositive area of the masking layer. These are as follows:

1. The layer may be given an additional sensitivity to infra-red, greenor deep ultra-violet. This sensitivity must stand up during negativedevelopment. The positive silver halide of the masking layer is thenflashed to infra-red, green or ultra-violet light and developed tosilver with an ordinary developer. Thereafter the positive dye imagesare formed in the remaining layers as usual by re-exposure andcolor-forming development.

2. The layer may contain incorporated, protected or non-difiusingcoupler compounds which iii may be broken down slowly either duringnegative development or can be removed by treatment not affecting thecolor. emulsion layers. Such couplers are esters of soluble couplerswhich may be broken down with alkali subsequent to negative developmentor couplers having an aldehyde group such as hydroxy benzaldehydes,solubilized by strong bisulfite solutions in a manner similar to thatdescribed in my U. S. Patent 2,269,146, granted January 6, 1942, Inaddition, alkali soluble protected couplers such as disclosed in Mannesand Godowsky, U. S. Patent 2,304,940, are useful. After removal of thecoupler from the masking layer the unexposed silver halide is exposed tolight to which it is the most sensitive, such as infra-red orultraviolet and the silver. image is developed in the layer. Insubsequent treatment following reexposure of the other layers andcoupler development, the silver images are removed with a silver solventsolution.

3. Easib' saponiflable esters of leuco dyes may be incorporated into themasking layer as couplers, as for instance,.the couplers disclosed inused. These compounds upon completion of their oxidation give dyes. Theesters of these bases are little soluble but the residue may be removedby s'aponification-from the positive area of the masking layer afterdevelopment of the negative dye image therein.

4. The mask layer may be composed of a finegrain silver chlorideprotected coupler emulsion. After negative development of the layer thepositive silver halide may be removed with strong sulfite solution. Inthis case it is generally advisable to place the mask layer as close tothe yellow filter layer as possible, or the filter dye may even beincorporated in the mask layer, and

the other emulsion layers should be slow speed moval of the residualsilver halide in the mask layer is then necessary.

6. A fast red sensitive auto-positive emulsion with or withoutadditional sensitivity in the infra-red, or ultra-violet may be used inthe masking layer. The red positive in the mask layer develops in thenegative developer along with the other negatives. The masking layer maythen be flashed to infra-red light or ultra-violet and developed in acoupling developer producing a dye image of the chosen color, preferablygray. If the appearance of the transparency is no object I the negativesilver halide in the mask layer may be flashed to red 'light along withthe red sensitive color emulsion layer and both developed to cyan. Theremaining dye images may be formed in the film by any chosen method, asfor instance,

by means of color-forming development. In printing from a transparencyof this type an amount of green light equivalent to the red mask overthe highlightsmust be added to the printing light preferably by using anequivalent green filter. It is essential in this case that the contrastand maximum density of tlie cyan color positive be raised so that theresultant gamma of the red negative red mask and the cyan positive beequal to that of the magenta and yellow positive gamma taken'separately.

'In the above-described methods of producing masking images in themasking layer, the sensitometric characteristics of the masking imagemay obviously be controlled in several ways. For instance, if the redsensitive emulsion layer ii of Fig. 1' has high or low red sensitivityas compared to the sensitivity level of the other layers, the density ofthe resultant masking image will be easily controllable. the emulsion isof high or low contrast, gamma characteristics of the masking image arealso controllable.

In a variation of my method wherein it is desired that the masking imagebe controlled by the green subject during initial exposure, to correctfor incorrect absorption of the magenta dye, a green sensitivity may beconferred to the masking emulsion layer in addition-to the redsensitivity, or a separate masking layer of green sensitivity may beprovided. Also, separate masking layers are not essential in that, ifdesired, the silver halide designed to receive the masking exposure maybe incorporated in one of the picture emulsion layers. The maskingemulsion layer may also be blue sensitive, but our preferred methodsinclude only green and red sensitivity for the emulsion.

In another arrangement the masking layer is coated onto the back of thesupport opposite the red and green sensitive layer. The advantage ofusing a mask in such position, separated from the picture emulsionlayers by the width of the support, is that it gives the so-calleddiifus'ed masking effect. This diffused mask results in higher contrastin the reversal highlight areas and hence gives a better apparentdefinition. Another advantage of having the mask layer on Depending onwhether 1 the red or green aspect silver image in this mask emulsionlayer, the image on the heels part of the film upport may be toned.

\ My invention may also be applied tothe so-' called negative-positiveprocess of subtractive color photography in a manner now to be describedwith particular reference to Fig. 2 of the accompanying drawing. In thenegative-positive color process the blue absorption of the usual cyanand magenta, dyes gives a difierent result on the positive than will bearrived at when making a duplicate of an original color transparency.When printing from positive to positive, the blue absorption of the cyanand magenta. dyes'results in excess yellow on blues, greens and cyans inthe duplicate or print. In the negativepositive color process in whichthe blue, green and red aspect negatives of a multilayer film aredeveloped to yellow, magenta, and cyan negatives respectively, the blueand green absorptions of the cyan and the blue absorption of the magentadyes gives a different appearing positive. If such a color negative isprinted onto the same type of material the blue absorption of the cyannegative gives rise to a lack of yellow in the finished positive and acorrespondingly greater cyan density. In general, when a print is madeby the color-negative-to-color-positive process it will lack yellow andhave too much cyan. A masking method in this case to be successful musthold back the red printin onto the positive. Further, if one is toobtain better photographic scale as well as color masking, that is,decrease in contrast, the color negative must be masked in areascorresponding to the red and if necessary the green positives.

A film of the type described in Jelley and Vittum U. S. Patent2,322,027, granted June 15,

below the yellow filter layer, may bev used in this process. A filmconstructed in this manner, is shown in the first stage of Fig. 2 of theaccompanying drawing wherein a support IU of a cellulose ester orsimilar material carries red, green and blue sensitive emulsion layers24, 25, and 21 containing cyan, magenta and yellow couplers in therespective layers. The red' sensitive emulsion layer 26 has an'additional sensitivity to infra-red or ultra-violet and isdesigned toreceive a masking image. This layer contains a low contrast silverhalide emulsion but does not have any coupling compound therein. It isgenerally desirable to coat this layer as a thinner emulsion layer thanthe other layers. The red the back of the support is that processingopera- 1 tions may be carried out upon it with greater ease than wouldbe the case with a masking layer in position under the picture emulsionlayers. An anti-halation layer may be coated onto the masking layer inposition on the back of the support. An alternative method of processingthis type of diffused mask layer, in addition to the methods alreadylisted above, is that of toning. After the negative development, whichof course, develops sensitivity of the layer is designed to correct forthe blue and green light absorption of the cyan dye images and if it issensitized to green it will tend to correct for the us a1 [blueabsorption of the magenta dye.

After exposure of the film in a camera or printer, it is developed in adeveloping solution and coupler compounds masking layer.

remaining in the masking layer is exposed to infra-red light anddeveloped in a low contrast developing solution containingcolor-developing which, in'case the masking layer is only red andinfra-red sensitive and it is desired to correct only for incorrectabsorption of the cyan dye, would develop a red, orange or neutralcolored dye image in the masking layer. A developer 01 the type usefulin developing a red or orange image is the following:

Solution A 2-amlno-5-diethylamino toluene HCl grams 2 Sodium sulfite do-10 Sodium carbonate do .40 Potassium bromide do.. 4 Potassiumthiocyanate do.. 1 e-nitrobenzimidazole do 0.1 Water to -cc 950 Solution8 Cyanoacetanilide grams 0.8 Sodium hydroxide do 5 Water to -cc 50(Solution B is added to Solution A) A developer su'table for forming aneutral dye or protected silver image is the following:

2-amino-5-diethylamino toluene HCl grams 3 Sodium sulfite do 6 Sodiumcarbonate ..do 45 Potassium bromide do '1 Potassium thiocyanate do 1p-Benzyl phenol do 4 Sodium hydroxide do 5 Water to 1iters 1 Finally,the negative silver images are removed from the layers by use of aferricyanide'solution such as disclosed in U. S. Patent No. 2,252,718,followed by a hypo fixingsolution. The film appears as shown in thethird stage of Fig. 3 wherein the color emulsion layers contain the dyeimages 32, 34, and 35, colored yellow, magenta, and cyan respectively.The masking layer contains the positive dye image 33.

The negative color transparency is then printed upon a sensitive film orpaper of character similar to that shown in the first stage of Fig. 1except that the copying material has no The masked color negative whencolor corrected print will lighting the cyans and alused for printing athen be effective in.

' lowing more printing into the yellow emulsion layer of the copy toincrease the yellow, and the cyan printing will be held back.

It is to be noted. that a film constructed in the manner shown in thefirst stage of Fig. 2 of the drawing may be processed to give a colorpositive by the usual means of original exposure, negative developmentfollowed by reversal exposure and color-forming development. maskingimage comparable third stage of Fig. 1, i. e., a negative masking image,one means of doing this is to provide an autopositive red or greensensitive emulsion containing a suitable coupler for layer 26, theositive area of which will .develop during negative development alongwith the picture emulsion negatives; thereafter the layer may be exposedto red or green light at,the same time as the red or green sensitiveemulsions and developed to a dye image corresponding to the coupler wdalong with the given picture emulsion layer. The

to that shown in the 'included in my invention all modifications andequivalentsfalling within the scope of the ap- In order to form a Imasking emulsion layer'need not be placed be-.

tween the picture emulsions layers, but may be situated on the back ofthe film for reasons and advantages previously mentioned.

In a negative-positive process the masking layer in a film to bedeveloped to a color negative, in a manner similar to that previouslymentioned in respect to reversal color films, the layer may be coated onthe back of the film support with the added processing advantage ofenabling one to form a positive mask layer of silver iodide or othersimilar compound or metal which will not be removed during ordinarybleaching and fixing processes. In this method the film is first givencolor development whereby dye images are formed in the picture emulsionlayers and a negative silver image in the masking layer. The positivemasking image is then converted to silver iodide or similar compound bylocal application of for instance an iodide solution such as disclosedin my prior U. S. Patent 2,258,976 granted October 14, 1941. On theother hand the silver image may be toned to any othercompound or metalsuch as gold, uranium, Prussian blue etc. which will stand silverbleaching and fixing solutions.

In connection with my description of the method of forming mixed dyeimages in color films processed to color negatives, dye images of thistype are a great advantage over silver from the processing standpoint,in that they can be easily localized as negative or positive images,whereas negative and positive silver are difficult to separate. Dyeimagesv of this type may also be formed in films of the type shown inFig. l, in which case more than .one coupler compound is incorporated inthe masking emulsion layer.

In my invention as described herein and in the appended claims, wherethe sensitivity of the masking layer emulsion is either specified oronly described as being adapted to receive a masking image, it is to beunderstood that the sensitivity is that which will allow. recording ofan aspect of the original exposure, and in addition, permits treatmentof the layer during processing so that a masking image is formed only inthe region of the layer opposite in sign to the region of the coloredpicture images.

It is to be understood that the disclosure herein is by way of exampleand that I consider as pended claims.

What I claim is:

1. The method of forming a color correction image in a multilayer filmcarrying superposed silver halide emulsion layers each efiectivelysensitive-to only one of the primary colors, red, green and blue, andfree of coupler compounds, and a silver halide emulsion masking layerefiectively sensitive to at least one of said colors of longer wavelength than blue and containing a coupler compound capable of couplingwith the oxidation products of primary aromatic amino developing agentsand of producing a dye image which corrects for incorrect absorption oflight by dye images in said first-mentioned layers, which comprisesexposing the film to a colored subject, and simultaneously with theoriginal subject exposure, exposing the masking layer to the coloredsubject, and simultaneously developing silver images in all of thelayers so exposed and also simultaneously developing in the samedeveloping bath a dye image in the masking layer with a primary aromaticamino developing agent, tormposing the mm to a colored subject andsimuling positive dye images by color development of the residual silverhalide in the other layerstand removing the silver images and residualsilver halide from the layers.

2. The method of forming a color correction image in a multi-layer filmcarrying superposed silver halide emulsion layers each effectivelysensitive to only one of the primary colors, red, green and blue, andfree of coupler compounds, and a silver halide emulsion masking-layereifectively sensitive to at least one of said colors of longer wavelength than blue and containing a coupler compound capable of couplingwith the oxidation products of primaryaromatic amino developing agentsand oi producing a dye image which corrects for incorrect absorption oflight by dye images in said first-mentioned layers, 'the blue sensitivelayer being outermost and a yellow filter layer between the bluesensitive emulsion layer and the other layers, which comprises exlayers,and then removing the silver images and residual silver halide from thelayers.

taneously with the original subject exposure, exposing the masking andsimultaneously all of the layers so exposed and also simultaneouslydeveloping in the same developing bath a dye image in the masking layerwith a primary aromatic amino developing agent, forming positive dyeimages by color development: of the residual silver halide in thefirst-mentioned layers, the positive dye images in the first-mentionedlayers being complementary in color to the sensitivity of the respectivelayers, and the dye image in the masking layer being of a color whichcorrects the incorrect absorption of light by at least one of the dyeimages in the first-mentioned LE ROY M. anama.

layer to the colored'subject,

developing silver images in

